L-cysteine, an amino acid playing an important role in the metabolism of sulfur in all living organisms, is used not only in the synthesis of biological proteins such as hair keratin, glutathione, biotin, methionine, and other sulfur-containing metabolites, but also as a precursor for biosynthesis of coenzyme A.
Known methods of producing L-cysteine using microorganisms include: 1) a method of biologically converting D,L-ATC to L-cysteine using microorganisms, 2) a method of producing L-cysteine by direct fermentation using E. coli (EP0885962B; Wada M and Takagi H, Appl. Microbiol. Biochem., 73:48-54, 2006), and 3) a method of producing O-phosphoserine (“OPS”, hereinafter) by fermentation using microorganisms, and converting OPS into L-cysteine by reacting OPS with a sulfide under the catalytic action of O-phosphoserine sulfhydrylase (“OPSS”, hereinafter) (Korean Patent No. 1381048).
In particular, for the production of cysteine by the method 3) at high yield, the precursor, OPS, should be produced in excessive amounts. In this regard, the present inventors have made extensive efforts to discover an appropriate export factor that enables O-phosphoserine produced in an OPS-producing microorganism to be exported from cells smoothly.